1. Field of the Invention
The invention relates to an apparatus for measuring ions in a gas.
2. Description of the Art
The prior art discloses an apparatus for measuring ions in a gas in the form of an ion counter in which the sensor is constituted by a large and usually cylindrical capacitor with a gaseous dielectric. The gas in which the ion count is to be determined is passed through the capacitor. A high voltage is applied to the capacitor plates and the positive ions are deflected to the negatively charged plates and the negative ions to the positively charged plates where they give off their charge. The resulting current can be measured and constitutes a measure of the ion count.
In addition, an apparatus is known which makes it possible to measure the ion balance in that the gas flows past an electrode and the charge excess of one polarity on the electrode gives rise to a correspondingly directed measurable current. As the ion mobility is polarity-dependent, there is a charge equilibrium (ion balance) on the electrode in the case of somewhat differing ion densities in the gas.
Based on this prior art, the problem of the invention is to provide an apparatus for measuring ions in a gas which is small, takes up little space, gives rise to a minimum disturbance to the gas flow and is independent of the direction and speed of the flow, the sensor being connectable via a long cable to the processing electronics.